Discussion Forum

Hello, I want to determine dispersion diagram of 1D anisotropic photonic crystal. My unit cell (length a) is rectangular (2D geometry) three layer structure with alternating layer of isotropic and anisotropic material (y-axis direction). The two anisotropic layers differ in orientation of optics axis with respect to each other. I have doubt about the boundary conditions: I have given Floquet periodic BC (source and destination) in the direction of alternating layers (y-axis direction). The other two boundaries which are supposed to be continuous since my photonic crystal is 1D are given periodic continuity BC. I have noticed, if I increase the width (x-axis direction) of unit cell, the dispersion diagram consists of straight horizontal lines. If I change BC to PEC with the same width (longer or smaller), more number of straight lines appears. The smaller width of unit cell with continuity periodic boundary conditions given better dispersion diagram. How to avoid such solutions also is there a physical significance of such solutions? Can I use PML domain attached to the boundaries of unit cell where continuity periodic conditions (x-axis direction) are applied? I also see the solver only works for out-of-plane electric field component. When is try to run it for, in-plane component its gives the error: 'Maximum number of iterations reached. Eigenvalue solver interrupted. To all Eigen frequencies returned.’ Can you please suggest the solution to the above mentioned problems?